With the use of terminals, such as a smart phone and the like, an average amount of data used by mobile communication users has exponentially increased and users' demands for a higher data transmission rate also have continuously increased. A method of providing a generally high data transmission rate includes a method of providing a communication service using a wider frequency band and a method of increasing frequency usage efficiency. However, it is very difficult to provide a higher average data transmission rate through the method of increasing the frequency usage efficiency. It is because current communication technologies have already provided frequency usage efficiency close to a theoretical limit and further increasing the frequency usage efficiency through technology improvement is difficult.
Accordingly, providing the communication service through a wider frequency band is a realizable method of increasing the data transmission rate. At this time, it is required to consider an available frequency band. In view of the current frequency distribution policy, a band in which broadband communication of 1 GHz or more is possible is limited and a practically selectable frequency band is only the millimeter wave band of 30 GHz or more. In such a high frequency band, a base station using power equal to power used in a conventional cellular system has significantly reduced coverage in which a service is provided. In order to solve the above problem, a beamforming scheme that concentrates transmission or reception power in a narrow space to increase transmission or reception efficiency of an antenna is widely used.